The invention relates to an electronic module, more particularly a flat module comprising parallel strip conductors, i.e., flat electric conductors whose spacings from one another are much smaller than their widths. The strip conductors can, for example, serve as two-dimensional outgoing lines and two-dimensional return lines for a direct-current supply.
The knowledge of the manufacture and application of modules of this type, more particularly flat modules, has already substantially matured, but the invention described herein does offer significant improvement.
It is generally known that multilayer flat modules may contain several transmission line planes, one of said planes being a two-dimensional out-going line and another of the planes a two-dimensional return line for, e.g., a direct-current supply. The lines thus constitute strip conductors over which current-consuming components, e.g., specific gates, disposed on the module are supplied with the necessary direct voltage.
Such a module is, for example, described in the periodical publication "Computer Design," of February 1965, pp. 28-39, where the strip conductors of the direct-current supply constitute two adjoining planes D and C. By means of the two-dimensional construction of the direct-current supply a shielding effect is additionally desired between the timing pulse line accommodated in the plane D and the signal line planes mounted on the other transmission line plane C.
Similar arrangements are widely known, see e.g., "Electronics," May 13, 1960, pages 77-78, West German Unexamined Pat. application 1,132,202, FIGS. 2a and 4b; U.S. Pat. No. 3,300,686, FIGS. 10 and 11. The latter patent describes a module (large card 19) containing neighborning parallel transmission line planes disposed at regularly spaced distances from one another, of which the two outermost are the signal line planes and the two innermost the strip conductors for the direct-current supply. Here, too, the shielding function of the strip conductors is also utilized, namely, in conjunction with rapidly switching elements mounted on the module, of which interfering voltages are produced in the signal line planes due to the extraordinarily rapid switching of the elements, e.g., by switching processes lasting about 5 nanoseconds.
The interfering voltages produced by such rapid switching processes in the signal line planes of the module have also been investigated in the article published in the NTZ 1971, pp. 541-544, in particular as to the strength of the crosstalk between the signal lines of such a module.
In "Elektronische Rechenanlagen," 10, 1968, No. 4, pages 177-179, the influence of interfering voltages of a different kind is investigated by means of examination methods usually applied in high frequency engineering. These voltages are of a type which in the direct-current supply of flat modules in the event the components to be switched rapidly are accommodated in or on the flat module at great distance from the terminals on the module over which the direct-current supply for it is provided. It was at the same time assumed that the interfering voltages would depend on variations of the resistances of the direct-current supply inputs of the switching component. It was recommended as a remedial step that in the area of the terminals of the module a shunt capacitor be inserted between the strip conductors and a series resistance into one of the conductors of these strip conductors, namely in the area of the bridging capacitance. The series resistance is matched to the characteristic impedance of the strip conductors. This series resistance absorbs, because of its matching, the interfering voltage waves generated by the component and traveling along the strip conductors to the series resistance. To avoid excessive direct-current dissipation on this series resistance, it is, likewise, recommended that the characteristic impedance of the direct-current supply lines be made small so that the resistance valve of the series resistance can be made small. Apparently, particular attention was paid to cross sections of these direct-current supply lines which are illustrated in FIG. 3 of this publication and which already have a comparatively small characteristic impedance referred to lines normally employed in high-frequency engineering. Therefore, in this case the interfering voltages on the direct-current supply line are not already suppressed in the area of the switching element, but they are only prevented from being reflected and thereby from from frequently traveling back and forth between the component and the terminals or between the component and the battery. Thus, in this publication the interfering voltage travels only once from the component where it is generated to the series resistance which absorbs the interfering voltage. Hence, the remedial step of absorption in the area of the direct-current supply terminals of the module recommended here cannot prevent the interfering voltage from causing unwanted interferences in other components connected to the same direct-current line during its non-recurring travel from the component to the series resistance. What is prevented is that the interfering voltage remains active on the directcurrent supply line for a prolonged period in the absence of absorption.
It is furthermore to be noted that the strip conductors of the directcurrent supply shown in FIGS. 10 and 11 of U.S. Pat. No. 3,300,686 apparently have a still lower characteristic impedance than the lines recommended in FIG. 3 of the publication "Elektronische Rechenanlagen", 10. Thus, in the module shown in the U.S. patent referred to above a shunt capacitor could, where necessary, be placed in the area of the terminals along with a series resistance whose resistance value could be made still smaller than that which must be provided in the direct-current supply lines recommended in the publication "Elektronische Rechenanlagen," 10.
AEU 24, 1970, pages 263 to 268 reports on measurements which confirm that at the moment of switching a component connected to the directcurrent supply there arises extremely high, short-time interfering voltages on the direct-current supply lines. It is true that in this reference these interfering voltages are attributed to the saturation of the modules provided in the gate and connected with the edge steepness of the direct-current change in the direct-current supply for the electronc components, particularly the transistors, provided in the gate. This, of course, contradicts the investigations reported in the above mentioned publication "Elektronishe Rechenanlagen," 10, where such interfering voltages are attributed to the change in the resistance of the direct-current supply inputs of the component upon the switching thereof. The difference between the two reasons for the generation of such interfering voltages is relatively small, because also the relevant edge steepness of the direct-current variation caused by the saturation can be interpreted as a time-controlled, even if continuous, variation of the resistances at the direct-current supply inputs of the component.
The investigations referred to in the above identified publication "AEU" have shown that the interfering voltages would, above all, also depend on the inductance of the direct-current supply lines. It is particularly disturbing, according to this publication, if this inductance is large, i.e., if the length of the direct-current supply lines is comparatively large. The remedial measure recommended therein consists in connecting shunt capacitors of very high capacitance C1, C2, C3 directly to the direct-current supply inputs of the component part (see FIG. 15). These cause a rapid attenuation of the interfering voltages in conjunction with resistors R disposed in the component (see particularly page 268, left-hand column, last paragraph, to the end of the right-hand column). The interfering voltages then scarcely diffuse to the direct-current supply lines but are largely suppressed on the site where they are generated.
There are also flat modules comprising parallel strip conductors with spacings much small than the widths thereof, whereby the strip conductors constitute the two-dimensional outgoing line and return line of the directcurrent supply. In this case, the strip conductors are bridged by shunt capacitors of very high capacitance, e.g., several uF, at specific points lying not directly at the direct-current supply inputs of the components and also not only in the area of the terminals of the component. In this case, not only one of the two strip conductors, but also the other strip conductor serves to diffuse reference potentials to which the signals of the signal lines are referred. Due to the shunt capacitors of extremely high capacitance, practically none of the high-frequency interfering voltages can be diffused without hindrance, because these bridged strip conductors constitute a low-pass filter with too low a cut-off frequency. The low-pass filter in this case essentially consists of series inductances produced by the self-inductance of the strip conductor segments between the shunt capacitors or between strip conductor edge and neighboring shunt capacitor, and of shunt capacitances produced essentially by the shunt capacitors.
It is, therefore, an object of the invention to provide means for suppressing interfering voltages that appear and could diffuse to the direct-current supply strip conductors in the course of switching processes in component parts, e.g., in gates, without the necessity of additionally providing the above mentioned remedial measures, namely, attenuated shunt capacitors of very high capacitance connected directly to the direct-current supply inputs of the switching elements and/or one or more shunt capacitors of very high capacitance in conjunction with a series resistance matched to the characteristic impedance of the direct-current supply strip conductors and located in the area of the terminals of the module. Such shunt capacitors of very high capacitance shall, as well, not be provided alongside the strip conductors. However, the solution in accordance with the invention shall in special cases permit the additional provision of at least the two prior art remedial measures first mentioned whereby, however, the shunt capacitors to be provided need only have smaller capacitances than would otherwise be necessary if said prior art remedial measures are applied. Moreover, it must also be possible to employ the direct-current strip conductors at the same time and at least partly for the shielding between different signal planes.